ENSO Atmospheric Teleconnections

Abstract

The El Niño Southern Oscillation (ENSO) causes climatic fluctuations in the tropics and extratropics via atmospheric teleconnections. The anomalous Pacific sea surface temperatures associated with ENSO modulate the Walker and Hadley circulations, causing profound impacts on rainfall and temperature over land and oceans. Globally, El Niño events usually lead to a short‐term rise in averaged temperatures while global‐mean temperatures typically decrease during La Niña events. In addition, during El Niño events, anomalously dry conditions are generally observed in the Maritime Continent, Australia, northern South America, southern Asia, and southern Africa, while anomalously wet conditions typically occur in southwestern North America, western Antarctica, and eastern Africa. While the global effects of La Niña are roughly of opposite sign, this is not true for all regions. This nonlinearity of ENSO atmospheric teleconnections is caused by variations in the location of the anomalous equatorial warming superimposed on the Pacific mean state and interactions of ENSO with off‐equatorial regions and other ocean basins, as well as with the annual cycle and other modes of climate variability. Furthermore, nonstationary behavior of ENSO teleconnections can occur either due to stochastic variability or deterministic low‐frequency modulations. As the world warms in response to greenhouse gas forcing, climate model projections suggest changes of the Pacific mean state that can intensify ENSO‐driven precipitation variability in the Pacific and many regions beyond. © 2021 American Geophysical Union. Published 2021 by John Wiley & Sons, Inc.